Development of exposed photographic silver halide elements

ABSTRACT

A PHOTOGRAPHIC SILVER HALIDE EMULSION IS DESCRIBED WHICH COMPRISES A COMPOUND OF THE FORMULA:   1,2-DI(RO-),(R2-S-),R1-BENZENE   WHEREIN: R IS HYDROGEN, ACYL, HALOACYL OR ACYL CARRYING A QUARTERNARY AMMONIUM GROUP, R1 IS HYDROGEN, ALKYL, ARYL, HALOGEN OR ALKOXY, AND R2 IS AN ALIPHATIC, AROMATIC OR HETERCYCLIC GROUP. THE COMPOUNDS ARE ESPECIALLY USEFUL IN LIPPMANNEMULSIONS TO REDUCE DISTORTIONS OF IMAGE DETAILS, TO ENHANCE IMAGE SHARPNESS AND TO REDUCE YELLOW STAINING UPON REVERSAL DEVELOPMENT.

United States Patent 3,825,426 DEVELOPMENT OF EXPOSED PHOTOGRAPHIC SILVER HALIDE ELEMENTS Robert Joseph Pollett, Vremde, Herman Adelbert Philippaerts, Edegem, Antoon Leon Vandenberghe, Hove, and Jozef Frans Willems, Wilrijk, Belgium, assignors to AGFA-Gevaert N.V., Mortsel, Belgium No Drawing. Filed Nov. 3, 1972, Ser. 110. 303,404 Claims priority, application Great Britain, Nov. 10, 1971, 52,290/71 Int. Cl. G03c 1/34, 1/78 U.S. CI. 96-76 R 8 Claims ABSTRACT OF THE DISCLOSURE A photographic silver halide emulsion is described which comprises a compound of the formula:

S-Rz

wherein:

R is hydrogen, acyl, haloacyl or acyl carrying a quaternary ammonium group,

R is hydrogen, alkyl, aryl, halogen or alkoxy, and

R is an aliphatic, aromatic or heterocyclic group.

The compounds are especially useful in Lippmannemulsions to reduce distortions of image details, to enhance image sharpness and to reduce yellow staining upon reversal development.

The present invention relates to the use in silver halide photography of compounds which on development release aliphatic, aromatic or heterocyclic mercaptans and to the use of these compounds in silver halide emulsions, especially silver halide emulsions of the Lippmann type.

Lippmann emulsions, normally having an average grainsize of less than 100 nm., are of particular importance for the preparation of photographic plates or films with high resolution, for use in micro-photography, for recording nucleophysical phenomenons, for the preparation of masks in the production of microelectronic integrated circuits, for use in holography, for high-density data storage, etc.

In the production of microelectronic integrated circuits, drawings are made on highly enlarged scale of the various successive masks necessary to produce one integrated circuit whereupon the drawings are reduced if necessary in successive steps, and reproduced on a photographic Lippmann plate or film material forming thereby the mask ready for use. By various photographic and chemical steps (photo-etching of lacquered plates) the images of the masks thus produced are transferred to the surface on which the integrated circuit is to be made, in order to produce the required circuit elements.

The photographic materials for use in the production of masks as described above should have a high resolving power and accutance, and allow a correct reproduction of the dimensions of the image. However, with highresolution Lippmann-materials special problems are encountered both on reversal and negative processing. For instance, the images produced often show at certain areas distortions of image details by mutual influence of closely adjacent image details and the image-sharpness does not always meet the requirements.

It has now been found that the above disadvantageous effects can be reduced or eliminated by incorporating in Patented July 23, 1974 the Lippmann-emulsions pyrocatechol derivatives corresponding to the following general formula:

S-Rz wherein:

R stands for hydrogen, acyl, e.g. acetyl, haloacyl, e.g. haloacetyl or acyl carrying a quaternary ammonium p,

R is hydrogen, alkyl, aryl, halogen or alkoxy, and

R is an aliphatic group, more particularly alkyl including substituted alkyl e.g. alkyl substituted with carboxy, with aryl or with a heterocycle, an aromatic group more particularly aryl including substituted aryl e.g. aryl substituted with halogen or with C -C alkyl, or preferably a heterocyclic group e.g. a l-substituted S-tetrazolyl or 3-triazolyl group or a Z-beuzothiazolyl group.

Representative examples of compounds corresponding to the above general formula and suitable for use according to the present invention are:

Compounds 6 and 7 are of incompletely determined structure as to the position of the heterocyclic thio group; this is indicated by the use of x instead of an integer in the structure, though it is presumed that the position is the 4-position.

The compounds of the above general formula wherein R is not H are the chemically masked forms of those wherein R is H and can be prepared from the latter by methods described in the literature e.g. U.S. Pat. 3,246,988 and Belgian Patent Specification 734,140. The pyrocatechol derivatives that besides the thio group carry a group R other than H e.g. alkyl, aryl, alkoxy etc. can be prepared as is illustrated in J. Org. Chem. 29 (1964) 589 by allowing to react the correspondingly substituted o-benzoquinone with the appropriate aliphatic, aromatic or heterocyclic thiol. Since the unsubstituted o-benzoquinone (R H) is unstable this method is less satisfactory for the preparation of the hitherto unknown pyrocatechol derivatives wherein R is H. It was found that the novel pyrocatechol derivatives wherein R is H and R is a heterocycle can be prepared satisfactorily by reaction of the heterocyclic mercapto compound with o-benzoquinone formed in situ from pyrocatechol and an oxidizing agent, e.g. potassium hexacyanoferrate(III).

In the following preparations it is illustrated how compounds 5 to 8 were prepared.

Preparation 1: Compound 5 To a solution of 13 g. (0.118 mole) of pyrocatechol, 17.8 g. (0.1 mole) of 1-phenyl-S-mercaptotetrazole add 50 g. of sodium acetate-3 water in 180 ml. of water, a solution of 65 g. (0.2 mole) of potassium hexacyanoferrate(III) and 50 g. of sodium acetate-3-water in ml.

of water was added at room temperature with stirring. The mixture Was stirred for 1 hour whereupon the precipitate was filtered off by suction and recrystallized from 200 ml. of methanol.

Yield: 20 g. (70%). Melting point: 164 C.

Preparation 2: Compound 6 To a mixture of 13 g. (0.118 mole) of pyrocatechol and 16.7 g. (0.1 mole) of 2-mercaptobenzothiazole in 150 ml. of acetone and 50 g. of sodium acetate-3-water in 50 ml. of water, a solution of 65 g. (0.2 mole) of potassium hexacyanoferrate(III) and 50 g. of sodium acetate-3-water in 150 ml. of water was added with stirring at 15 C. The mixture was stirred for 30 min. whereupon the precipitated salts were filtered off and the filtrate poured into water. The precipitate was purified by continuous extraction with methylene chloride/methanol (10:1).

Yield: 14 g. (51%). Melting point: 196 C.

Preparation 3: Compound 7 To a suspension of 17.7 g. (0.1 mole) of 1-pheny1-3- mercapto-1,2,4-triazole in 400 ml. of methanol, a solution of 0.114 mole of o-benzoquinone (Ber. 37, 4745) in 750 ml. of anhydrous ether is dropwise added in 20 min. with stirring at 10 C. The quinone solution decolorized and the precipitate dissolved almost completely. After 1 hour the solution was filtered and concentrated by evaporation. The residue was recrystallized from a minimum amount of methanol.

Yield: 11.5 g. (40%). Melting point: 198 C.

Preparation 4: Compound 8 To a solution of 28.6 g. (0.1 mole) of compound 5 in 120 ml. of dioxan comprising 2.4 g. (0.1 mole) of magnesium curlings, 39 g. (0.5 mole) of acetyl chloride were dropwise added in 30 min. with stirring and while refiuxing. The mixture was refluxed for 24 hours and then filtered. The filtrate was evaporated and the residue extracted with 100 ml. of benzene. The non-soluble residue was isolated whereas the benzene solution was filtered and evaporated.

Yield: 34 g. (92%). Melting point: 50 C.

Both in reversal and negative development the use of the compounds of the above formula results in an enhancement of the image sharpness, particularly sharpness of fine detail, and in a favourable effect on the distortions of image-details. In addition thereto, where reversal processing of Lippmann material is very critical and often gives rise to yellow staining, probably owing to residual oxidation products of the developing agent, it was found that the compounds of the above general formula counteract said yellowing.

The compounds for use in accordance with the present invention are incorporated in the emulsion layer by addition, as a solution or dispersion, to the coating compositions of the Lippmann emulsion.

The concentration of the compounds used according to the invention depends on the characteristics of both the chosen compound and the emulsion and is therefore best determined by trial. In most cases the optimum concentration in the silver halide emulsion is between about 20 mg. and about 2 g., preferably between about 100 mg. and 1 g. per mole of silver halide.

The thickness of the emulsion layer of a photographic material according to the present invention is generally comprised between about 3 microns and about 8 microns, and the average grain size of the silver halide grains is generally less than 80 nm. The ratio of silver halide to hydrophilic colloid binder in the Lippmann emulsion according to the present invention is preferably at least 1:2 and at most 4: 1.

The silver halide Lippmann emulsions may be prepared according to methods well known in the art and described in the literature (see e.g. P. Glafkides Photographic Chemistry, Vol. I, 1958, pages 365-368, Mees/ James The theory of the Photographic Process, 1966, p. 36 and National Physical Laboratory Notes on Applied Science No. 20: Small Scale Preparation of Fine- Grain (Colloidal) Photographic Emulsions, B. H. Crawford, London, 1960). They may also be prepared according to the technique described in co-pending United Kingdom Patent Application 15,948/70.

Silver halide Lippmann-emulsions with very fine grain can be obtained by effecting the precipitation of the silver halide in the presence of heterocyclic mercapto compounds as described in United Kingdom Patent Specification 1,204,623 or in the presence of compounds as described in co-pending United Kingdom Patent Applications 53,025/69 and 54,539/69.

The hydrophilic colloid used as the vehicle for the silver halide may be any of the common hydrophilic colloids employed in photographic light-sensitive emulsions for example, gelatin, albumin, zein, casein, alginic acid, a cellulose derivative such as carboxy-methyl cellulose, a synthetic hydrophilic colloid such as polyvinyl alcohol and poly-N-vinylpyrrolidone, etc. If desired compatible mixtures of two or more colloids may be employed for dispersing the silver halide.

Various silver salts may be used as the light-sensitive salt such as silver bromide, silver iodide, silver chloride, or mixed silver halides such as silver chlorobromide, silver bromoiodide and silver chlorobromoiodide. Silver bromide emulsions which may have an iodide content of at most 8 mole percent and having an average grain-size of at most nm. are favoured.

The emulsions may be coated on a wide variety of photographic emulsion supports. Typical supports include cellulose ester film, polyvinyl acetal film, polystyrene film, polyethylene terephthalate film and related films of resinous materials as well as paper and glass. In the manufacture of high-resolution plate materials for the preparation of masks for use in the electronic industry, glass supports are most advantageously used in view of their high dimensional stability.

The light-sensitive silver halide emulsions of use in the preparation of a photographic material according to the present invention may be chemically as well as spectrally sensitized.

They may be spectrally sensitized by any of the known spectral sensitizers such as cyanines and merocyanine dyes for photographic light-sensitive silver halide materials. The silver halide emulsions for microelectronic mask making according to the present invention are most advantageously sensitized for the green region of the spectrum. The exposure light is preferably chosen so that it radiates light of a wavelength to which the emulsion has been spectrally sensitized.

They may be chemically sensitized by effecting the ripening in the presence of small amounts of sulphur containing compounds such as allyl thiocyanate, allyl thiourea, sodium thiosulphate, etc. The emulsions may also be sensitized by means of reductors for instance tin compounds as described in French Patent Specification 1,146,955 and in Belgian Patent Specification 568,687, imino-amino methane sulphinic acid compounds as described in United Kingdom Patent Specification 789,823 and small amounts of noble metal compounds such as gold, platinum, palladium, iridium, ruthenium and rhodium.

The said emulsions may also comprise compounds which sensitize the emulsion by development acceleration for example compounds of the polyoxyalkylene type such as alkylene oxide condensation products as described among others in US. Pats. 2,531,832 and 2,533,990, in United Kingdom Patent Specification 920,637, 940,051, 945,340 and 991,608 and in Belgian Patent Specification 648,710 and the known onium compounds including quaternary ammonium, quaternary phosphonium and ternary sulphonium compounds as well as onium derivatives of amino-N-oxides as described in United Kingdom Patent Specification 1,121,696.

Further the emulsions may comprise stabilizers e.g. heterocyclic nitrogen-containing thioxo compounds such as benzothiazoline-Z-thione and 1-phenyl-2-tetrazoline-5- thione and compounds of the hydroxytriazolopyrimidine type. They can also be stabilized with mercury compounds such as the mercury compounds described in Belgian Patent Specifications 524,121 and 677,337, United Kingdom Patent Specification 1,173,609 and in US. Pat. 3,179,520.

The emulsions may also comprise light-absorbing dyes which are so chosen that they absorb light of the Wavelength to which the material is exposed so that scattering and reflection of light within the photographic material is reduced. For more details regarding these dyes there can be referred to Belgian Patent Specification 699,375 and co-pending United Kingdom Patent Application 58,844/ 68. The dyes are preferably used in such amounts that per micron of emulsion layer thickness a density comprised between 0.05 and 0.20, measured in the spectral region of the exposure light, is obtained.

Any of the hardening agents for hydrophilic colloids may be used in the emulsions according to the present invention such as chromium, aluminium, and zirconium salts, formaldehyde, dialdehydes, hydroxy aldehydes, acrolein, glyoxal, halogen substituted aldehyde acids such as mucochloric acid and mucobromic acid, diketones such as divinyl ketone, compounds carrying one or more vinylsulphonyl groups such as divinyl sulphone, 1,3,5- trivinylsulphonyl benzene, hexahydro-s-triazines carrying vinylcarbonyl, halogenoacetyl and/or acyl groups such as 1,3,S-triacryloyl-hexahydro-1,3,5-triazine, 1,3 diacryloyl 5 acetylhexahydro 1,3,5 triazine, 1,3,5 trichloroacetylhexahydro-1,3,5-triazine, etc.

In order to promote adhesion of the emulsion to glass supports in the preparation of high resolution plate materials, the silicon compounds described in co-pending United Kingdom Patent Application 54,678/68 can be incorporated into the emulsion.

The light-sensitive emulsions may also comprise all other kinds of ingredients such as plasticizers, coating aids, etc.

Though the compounds corresponding to the above general formula have been particularly described for use in Lippmann-emulsions they can also be used in other light-sensitive silver halide emulsions to promote enhanced sharpness. The compounds of the invention are silver halide developing agents and release development inhibiting mercaptans. Thus, they may be used in X-ray and other non-optically sensitized emulsions as well as in orthochromatic, panchromatic and infrared-sensitive emulsions. Further, they may be used in emulsions intended for use in the well known silver complex diffusion transfer process.

They are particularly useful in emulsions intended for colour photography where, during development, on the exposed areas the oxidized aromatic primary amino colour developing agent couples with a colour forming coupler to form a dye image. By the presence of the compound of the invention in the emulsion, the development inhibitor is image-wise released which results in reduced graininess and the pyrocatechol developer locally regenerates the aromatic primary amino colour developing agent from its oxidation products.

The following examples illustrate the present invention.

EXAMPLE 1 A silver bromide emulsion comprising per kg. 72 g. of silver bromide and 93 g. of gelatin was prepared by simultaneous addition of a silver nitrate solution and a potassium bromide solution to a 3% aqueous solution of gelatin. The conditions of precipitation were adjusted so that a Lippmann emulsion with an average grain size of 70 nm. was obtained. Details as to the preparation of Lippmann-emulsions can be found amongst others in P. Glafkides Photographic Chemistry, Vol. I, 1958, Fountain Press, London.

The emulsion was sensitized by addition of 150 mg. per g. of silver halide of a merocyanine dye by means of which a strong spectral sensitization in the region of 520-550 nm. was obtained. Then, an amount of the light-absorbing dye having the following structural formula:

was added so as to obtain, after the emulsion is coated, a density of 0.10 per micron of emulsion layer thickness, measured at 550 nm. (absorption maximum of the lightabsorbing dye used).

The emulsion was divided into 2 portions and to one of these portions compound 5 was added in an amount of 500 mg. per mole of silver halide.

The emulsion portions were coated on glass plates pro rata of 230 ml. per sq. In. so as to obtain after drying a layer thickness of 6 microns. The 2 plate materials A and B were then exposed under identical circumstances by means of monochromatic light, the spectral composition of which corresponds with the absorption region of the light-absorbing dye used, through a test pattern, as normally used for the quantitative evaluation of materials for use in microelectronics mask-making, consisting of lines which are separated by spaces of the samewidth as the lines themselves and with a width varying from 1 to 20 The exposure was of such an intensity so as to limit the density in the transparent areas of the images produced, which correspond with the white lines of the test pattern, to the fog value.

After the exposure the 2 plate materials were reversal processed at 20 C., under completely identical circumstances.

For that purpose the exposed materials were first developed for about 5 min. in the following developing liquid the pH of which was adjusted to 10.5

Hydroquinone 2 Monomethyl-p-aminophenol hemisulphate 4 Potassium bromide 2 Sodium carbonate 40 Sodium sulphite 40 Potassium thiocyanate 5 Water to make 1 litre.

After rinsing for some minutes in water the materials were treated for 5 minutes in a clearing bath of the following composition:

Sodium sulphite g 100 Water to make 1000 ccs.

After rinsing again for some minutes the materials were subjected to an overall exposure in order to render the residual silver bromide developable whereupon they 7 were treated for about 6 minutes in the following developing liquid:

G. Hydroquinone Monomethyl-p-aminophenol hemisulphate 1 Sodium sulphite 40 Sodium carbonate 30 Potassium bromide 0.5

Water to make 1000 ccs.

EXAMPLE 2 Example 1 was repeated with the dilference that materials A and B were processed so as to obtain a negative image by means of a developing liquid of the following composition:

Water ml 800 Monomethyl-p-aminophenol' hemisulphate g 1.5 Sodium sulphite (anhydrous) g 25 Hydroquinone g 6 Sodium carbonate (anhydrous) g 40 Potassium bromide g 1 Water to make 1 litre.

As compared with material A, material B showed improved image-sharpness and less distortions in line-reproduction.

We claim:

1. Photographic silver halide emulsion comprising a compound of the general formula:

8 wherein: R is hydrogen, acyl, haloacyl or acyl carrying a quaternary ammonium group, R, is hydrogen, alkyl, aryl, halogen or alkoxy, and R is an aliphatic, aromatic or heterocyclic group.

2. Photographic silver halide emulsion according to claim 1, wherein in the formula R stands for a l-substituted S-tetrazolyl or 3-triazolyl group or for a 2-benzothiazolyl group.

3. Photographic silver halide emulsion according to claim 1, wherein said emulsion is a Lippmann-emulsion having an average-grain size of less than 100 nm.

4. Photographic silver halide emulsion according to claim 3, wherein the said compound is present in an amount comprised between 20 mg. and 2 g. per mole of silver halide.

5. Photographic silver halide emulsion according to claim 3, wherein the ratio of silver halide to hydrophilic colloid binder in the Lippmann-emulsion is comprised between 1:2 and 4: 1.

6. Photographic emulsion according to claim 3, wherein the said emulsion is a silver bromide emulsion which may comprise silver iodide in an amount of at most 8 mole percent and which has an average grainsize of at most nm.

7. Photographic material comprising a support and an emulsion according to claim 1.

8. Photographic material according to claim 9, wherein the said support is a glass support.

References Cited UNITED STATES PATENTS 3,700,457 10/1972 Youngquist 96-114.1

RONALD H. SMITH, Primary Examiner A. T. SURO PICO, Assistant Examiner US. Cl. X.R. 

